1. Field of the Invention
The invention relates to compositions comprising specific polysiloxane copolymers, to processes for preparing them, and also to their use as defoamers, particularly for defoaming aqueous surfactant formulations.
2. Description of the Related Art
In many liquid systems, especially aqueous systems, which include surface-active compounds as desired or else unwanted constituents, it is possible for problems to occur as a result of foaming if these systems are contacted more or less intensively with gaseous substances, such as during the gassing of waste waters, during the intensive stirring of liquids, during distillation, washing or coloring operations or during dispensing processes, for example.
This foam can be controlled by mechanical means or through the addition of defoamers. Siloxane-based defoamers have proven particularly appropriate here. Siloxane-based defoamers are prepared in accordance with DE-B 15 19 987, for example, by heating hydrophilic silica in polydimethylsiloxanes.
Defoamers based on polydimethylsiloxanes have the disadvantage that the compatibility of polydimethylsiloxanes with the majority of surfactant systems, such as wetting agents or liquid detergents, for example, is poor and the polydimethylsiloxanes tend to be deposited, which is highly undesirable.
These antifoam materials may be combined with polyethersiloxanes, as described in EP-A 341952, DE 102004052421, and DE 102005025450, for example. The polyethersiloxanes serve to improve the activity of the siloxane-based defoamers, which are considered unavoidable. The defoamer formulations, however, are likewise incompatible with aqueous surfactant systems and therefore are not suitable for application in storage-stable aqueous formulations, such as liquid detergents and wetting agents, for example.